Foot prosthesis having cushioned ankle

ABSTRACT

A simple, inexpensive prosthetic foot is provided incorporating a cushioned ankle including an ankle block formed of a resilient material or bladder having desired compliance and energy return characteristics. The ankle block is sandwiched between a foot element and an ankle element. One or more openings extends through the ankle block with a substantially transverse orientation relative to a forward walking motion. The size and shape of these openings, as well as the insertion of different types of stiffeners therein, provide desired performance characteristics to the ankle block. When the ankle block takes the form of one or more inflatable bladders, the pressure within these bladders is individually controlled by valves to provide desired performance characteristics to different portions of the prosthetic foot. A pump system can also be used to control and generate fluid pressure into these bladders. A preferred pump system generates fluid pressure based upon the movement of the amputee onto two telescoping pylons that are connected to the prosthetic foot.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of copending application Ser.No. 09/698,489, filed Oct. 26, 2000, which is a continuation-in-part ofapplication Ser. No. 09/138,357, filed Aug. 21, 1998, which claimspriority to provisional Application Serial No. 60/081,472, Apr. 10,1998. The entirety of each of these applications are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to prosthetic feet and, moreparticularly, to a simply constructed, low-profile prosthetic foothaving enhanced performance characteristics.

[0004] 2. Description of the Related Art

[0005] In the prosthetics market, the conventional SACH (solid-ankle,cushion-heel) foot has been the most widely prescribed artificial footover the past 35 years. The SACH foot generally includes a solid ankleand cushioned heel foot mounted to a limb along an approximate hingeaxis taken through the ankle. The SACH foot has been popular preciselyfor its simplicity, and thus economy, but includes certain drawbacks interms of dynamic response characteristics. Specifically, the low endSACH feet do not provide much energy storage and release, as do moresophisticated prosthetic feet.

[0006] Most modem foot prostheses incorporate some form of energystorage element for storing and releasing walking energy.Conventionally, this might consist of a spring-loaded ankle jointcomprising metal coil springs or, more commonly, rubber compliancemembers. Inexpensive foot prostheses have also been devised havingessentially a solid rubber or foam ankle block for storing and releasingwalking energy. Such an ankle block has been disclosed in my issuedpatent titled PROSTHESIS WITH RESILIENT ANKLE BLOCK, U.S. Pat. No.5,800,569, the entirety of which is incorporated by reference. A solid,compressible ankle block may be secured between upper and lower supportmembers to provide resilient compression and energy storage and release.The use of an ankle block member provides significant manufacturing andcost advantages. However, for certain applications it is difficult toattain a desired level of spring compliance and energy returncharacteristics using a solid ankle block due to the inherentlimitations of the materials involved in terms of elasticity, viscosityand maximum compression.

SUMMARY OF THE INVENTION

[0007] One embodiment of the present invention provides a simple,inexpensive prosthetic foot incorporating an ankle block havingselectable compliance and energy return characteristics that may bevaried over a wider range to accommodate the different weight, heightand activity level of amputees. The ankle block is formed ofcompressible material having desired compliance and energy returncharacteristics. The ankle block is sandwiched between a foot elementand an ankle element. One or more spring inserts are embedded inside theankle block to increase the rigidity of the prosthetic foot and toimprove the degree of energy storage and return. The shape of the springinserts is preferably one that supports compression during relativeangular rotation of the ankle plate and foot plate elements, such asduring toe and heel roll, and also vertical compression, such as inresponse to vertical shock loads.

[0008] In one aspect of the present invention, a basic prosthetic footis provided having enhanced performance characteristics generallycomprising a lower foot plate, an upper ankle plate, a foam ankle blockjoining the two plates, and a spring element embedded in the ankleblock. Both the foot plate and the ankle plate are constructed ofstrong, flexible material, preferably a laminate of composite material.The foot plate is sized approximately equal to a human foot beingreplaced, while the ankle plate has a similar width, but has a shorterlength than the foot plate. The ankle block has a length and widthapproximately equal to the ankle plate and is aligned therewith. Thespring element comprises two relatively flat carbon fiber compositemembers secured at their middle and separated at their ends. This givesthe spring element a preferable shape of a bow tie or double wishbone.Preferably, an attachment member couples the ankle plate to a stump orlower-limb pylon of the wearer. During walking, the combination of theresilient ankle block with embedded spring element and flexible platesprovides a smooth rollover from a heel-strike to a toe-off position.

[0009] In another aspect, the ankle block of a prosthetic foot may beprovided with cylindrical openings both in the fore and aft positions ofthe ankle block. These openings enable the placement of additionalinserts or stiffeners to give the block a desired rigidity. In apreferred embodiment, the foot element also has a tapered thickness.Further, the foot element comprises uplifted heel and toe ends and anarch region therebetween.

[0010] In another aspect, a prosthetic foot is provided comprising afoot plate element, at least one ankle plate element and an ankle blocksandwiched between the foot plate element and the ankle plate element.The foot plate element has a length approximately equal to the length ofa human foot, and comprises a resilient material capable of flexingalong its length. The at least one ankle plate element has a lengthsubstantially shorter than the foot plate element. The ankle blockcomprises a relatively soft, compressible material and providessubstantially the sole means of support and connection between the footplate element and the ankle plate element. At least one opening extendsthrough the ankle block with a substantially transverse orientationrelative to a forward walking motion. The foot plate element and theankle block flex in a cooperative manner to provide substantially smoothand continuous rollover transition from heel-strike to toe-off.

[0011] In another aspect, a prosthetic foot comprises a lower footplate, an upper ankle plate disposed above and generally over the lowerfoot plate and being spaced therefrom, and a plurality of inflatablebladders disposed between the upper ankle plate and the lower foot plateand separating the upper plate from the lower plate. The bladdersprovide substantially the sole means of support between the foot plateand the ankle plate. The foot plate and the bladder flex in acooperative manner to provide substantially smooth and continuousrollover transition from heel-strike to toe-off.

[0012] In another aspect, a prosthetic foot for connecting to a pylon ofan amputee is provided. The prosthetic foot comprises a foot plateelement having a length approximately equal to the length of a humanfoot, an ankle plate having a length substantially shorter than the footplate element, and at least one inflatable bladder between the ankleplate element and the foot plate element. The foot plate elementcomprises a resilient material capable of flexing along its length. Theat least one inflatable bladder provides substantially the sole means ofsupport and connection between the foot plate element and the ankleplate element. A fluid pump generates fluid pressure based on themovement of the amputee onto the pylon. A fluid pathway directs fluidinto the at least one inflatable bladder.

[0013] In another aspect, a pump system for a prosthetic foot isprovided. The system comprises at least one inflatable bladder, asyringe including a plunger and a cylinder, a fluid pathway connectingthe syringe to the at least one inflatable bladder, and a first pylonand a second pylon telescopingly engaged. The plunger is connected tothe first pylon and the cylinder is connected to the second pylon, suchthat relative movement between the first and second pylon moves theplunger in and out of the cylinder to generate pressure within the atleast one inflatable bladder.

[0014] In another aspect, a prosthetic foot is provided comprising aninner pylon and an outer pylon that are telescopingly engaged. Acompressible member is positioned in a chamber defined between the innerand outer pylons. The inner pylon moves relative to the outer pylon uponthe application and release of a compressive force onto the prostheticfoot. A fluid line is also provided in communication with the chamber.At least one inflatable bladder is in communication with the fluid line,and fluid pressure is generated in the at least one inflatable bladderbased on the relative movement between the inner and outer pylons. Inanother aspect, a prosthetic foot comprises a foot plate elementcomprising a resilient material capable of flexing along its length, andat least one ankle plate element. An ankle block comprising a relativelysoft, compressible material is sandwiched between the ankle plateelement and the foot plate element. The ankle block providessubstantially the sole means of support and connection between the footplate element and the ankle plate element. At least one opening extendsthrough the ankle block with a substantially transverse orientationrelative to a forward walking motion. At least one cam is inserted intothe at least one opening, the cam being rotatable to locally adjust thestiffness of the ankle block.

[0015] In another aspect, the prosthetic foot having a foot plateelement, at least one ankle plate element and an ankle block sandwichedtherebetween, includes a first and second chamber extending through theankle block. The first chamber is positioned in a fore portion of theblock and the second chamber is positioned in a rear portion of theblock, the first and second chambers being oriented generally transverseto a forward walking motion. First and second stiffeners are positionedin the first and second chambers, respectively, the first and secondstiffeners being moveable within each of said chambers.

[0016] In another aspect, a prosthetic foot is provided comprising afoot plate element comprising a resilient material capable of flexingalong its length, and at least one ankle plate element. An ankle blockcomprising a relatively soft, compressible material is sandwichedbetween the ankle plate element and the foot plate element. The ankleblock provides substantially the sole means of support and connectionbetween the foot plate element and the ankle plate element. The ankleblock includes a wedge cut-out in a rear portion of the ankle block. Inone embodiment, the prosthetic foot further comprises a wedge pieceinserted into the wedge cut-out.

[0017] In another aspect, the prosthetic foot comprising a foot plateelement, at least one ankle plate element and an ankle support membersandwiched therebetween is further provided with a strap connecting theankle plate element to the foot plate element. The strap is positionedbehind the ankle block relative to a forward walking motion and iscapable of adjusting the relative flexing properties between said ankleplate element and said foot plate element.

[0018] For purposes of summarizing the invention and the advantagesachieved over the prior art, certain objects and advantages of theinvention have been described herein above. Of course, it is to beunderstood that not necessarily all such objects or advantages may beachieved in accordance with any particular embodiment of the invention.Thus, for example, those skilled in the art will recognize that theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other objects or advantages as may be taught orsuggested herein.

[0019] All of these embodiments are intended to be within the scope ofthe invention herein disclosed. These and other embodiments of thepresent invention will become readily apparent to those skilled in theart from the following detailed description of the preferred embodimentshaving reference to the attached figures, the invention not beinglimited to any particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a perspective view of a prosthetic foot in oneembodiment of the present invention.

[0021]FIG. 2 is a cross-sectional view of a prosthetic foot in oneembodiment of the present invention.

[0022]FIG. 3 is a perspective view of a spring element embedded in theankle block in one embodiment of the present invention.

[0023]FIG. 4 is a side elevational view of a prosthetic foot moreclearly showing a foot plate having a tapered thickness along itslength.

[0024]FIG. 5A is a sectional view of a prosthetic foot in a heel-strikeposition of a walking stride.

[0025]FIG. 5B is a sectional view of a prosthetic foot in a flatposition of a walking stride.

[0026]FIG. 5C is a sectional view of a prosthetic foot in a heel-offposition of a walking stride.

[0027]FIG. 5D is a sectional view of a prosthetic foot in a toe-offposition of a walking stride.

[0028]FIG. 6 is a cross-sectional view of an alternative embodiment of aprosthetic foot of the present invention incorporating a modified springelement.

[0029]FIG. 7 is a cross-sectional view of another alternative embodimentof a prosthetic foot of the present invention incorporating a modifiedankle block.

[0030]FIG. 8 is a cross-sectional view of another alternative embodimentof a prosthetic foot of the present invention incorporating a modifiedankle block.

[0031]FIG. 9 is a cross-sectional view of another alternative embodimentof a prosthetic foot of the present invention incorporating aninflatable bladder ankle block.

[0032]FIG. 10 is a cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporating amultiple inflatable bladder ankle block.

[0033]FIGURE 11A is a partial cross-sectional view of anotheralternative embodiment of a prosthetic foot of the present inventionincorporating cylindrical slots.

[0034] FIGS. 11B-11D are perspective views of stiffeners that may beinserted into the cavities of the prosthetic foot of FIGURE 11A.

[0035]FIG. 12 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingdual ankle plates and cylindrical slots.

[0036]FIG. 13 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingtoe and heel air bladders.

[0037]FIG. 14 is a perspective view of the heel and toe bladders of FIG.13.

[0038]FIG. 15A is a perspective view of the components of anotheralternative embodiment of a prosthetic foot of the present inventionincorporating a shock pumping system.

[0039]FIG. 15B is a schematic view of the valve manifold of theprosthetic foot of FIG. 15A.

[0040]FIG. 16A is a perspective view of another alternative embodimentof a prosthetic foot of the present invention incorporating thecomponents of FIG. 15A.

[0041]FIG. 16B is a perspective view of one embodiment of a prostheticfoot incorporating a CO₂ cartridge.

[0042]FIGS. 17 and 18 are partial cross-sectional view of additionalalternative embodiments of a prosthetic foot of the present inventionincorporating chambered urethane.

[0043]FIG. 19 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingrotatable cams.

[0044]FIG. 20 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingan actuator and moveable stiffeners.

[0045]FIG. 21 is a partial cross-sectional view of another alternativeembodiment of a prosthetic foot of the present invention incorporatingan adjustable strap and an insertable heel wedge piece.

[0046]FIG. 22 is a partial cross-sectional view of the prosthetic footof FIG. 21, further illustrating a C-shaped insert for tightening theadjustable strap.

[0047]FIG. 23 is a partial cross-sectional view of prosthetic foothaving an inflatable bladder in fluid communication with an active shockmodule.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] With reference to FIGS. 1 and 2, a first embodiment of aprosthetic foot 10 of the present invention is shown in a perspectiveview and a cross-sectional side view, respectively. The prosthetic foot10 generally comprises a lower foot plate 12, an upper, smaller ankleplate 14, an ankle layer or block 16 made of resilient material,connecting the foot plate 12 to the ankle plate 14, and a spring element18 embedded within the ankle block 16. The foot plate 12 has a lengthand width roughly equal to the approximate length and width of theparticular wearer's amputated foot and sized to fit within an outer,flexible cosmesis 30, shown in phantom. The ankle plate 14 and theresilient ankle block 16 have approximately the same horizontalcross-sectional size. The ankle plate 14, ankle block 16, and springelement 18 are centered transversely with respect to and are generallypositioned over the back half of the foot plate 12. The ankle block 16is sandwiched between the foot plate 12 and the ankle plate 14 and ispreferably glued or bonded to both plates using polyurethane adhesive orother known securement technologies.

[0049] The spring element 18 is a resilient support member insertedwithin the resilient ankle block 16. As shown in FIG. 3, the springelement 18 is preferably comprised of upper and lower plate-like members22 and 24, each of which is relatively flat and has a substantiallyrectangular vertical projection. These members are secured at theircenter by a fastener 26 and separated at ends 80 and 82. The uppermember 22 preferably has a curvilinear concave upward shape, while thelower member 24 preferably has a curvilinear concave downward shape.This gives the spring element 18 a substantially double wishbone or bowtie shape.

[0050] As shown in FIG. 1, the spring element 18 is completely embeddedwithin the ankle block 16 so as not to be visible from the outside.Referring to FIG. 2, the spring element 18 extends substantiallylongitudinally across the length of the ankle block 16, and has a widthsubstantially equal to the width of ankle block 16. The fastener 26 maycomprise bolts, a weld, or any other fastening means as would be knownto those skilled in the art. In the preferred embodiment, the fastener26 is a strap which is laminated around the center portion of the twomembers 22, 24. A wedge member 28, preferably of a resilient elastomer,is placed between the two plate members 22, 24 to protect the innersurfaces of the members and to provide additional support to the springelement 18. The wedge 28 acts to provide leverage between the two platemembers 22, 24, and enables adjustment of the flexing characteristics ofthe spring element 18, if desired. Alternatively, it may be bondedpermanently in place or formed integrally with one or both of the platemembers 22, 24, as desired. Although the spring element 18 has beendescribed as having a double wishbone or bow tie configuration, othershapes and sizes may be appropriate for providing support to the ankleblock 16. Furthermore, more than one spring element may be provided inthe ankle block to provide support and energy return to the prostheticfoot 10.

[0051] As can be seen in FIGS. 1 and 2, the prosthetic foot 10 furthercomprises a pylon member 32 which can be secured to the stump of theamputee (not shown) and extends relatively downward therefrom in agenerally vertical direction. The pylon member 32 in the preferredembodiment is of tubular construction having a substantially equalmoment of inertia in all directions to restrict bending in alldirections. The tubular member 32 is also preferably hollow so that itis relatively light in weight and utilizes less material which reducesthe cost of production. The pylon member 32 is dimensioned so as to beinterchangeable with a standard 30 mm pylon. Other configurations whichimpart rigidity, such as rectilinear cross sections having relativelylarger moments of inertia about one or both transverse axes can also beutilized to obtain the benefits discussed herein. A centerline 70through pylon 32, shown in FIG. 1, defines the downward direction of theapplication of force.

[0052] As shown in FIGS. 1 and 2, the ankle plate 14 is secured to thepylon member 32 through a vertically oriented upper attachment member34. The upper attachment member 34 is attached to a curvilinear anklesection 36, which is connected to the ankle plate 14. Preferably, thesethree pieces are monolithically formed with one another for optimumstrength and durability. The attachment member 34 has a rearward surface38, as shown in FIG. 2, and a forward surface 40 substantially parallelthereto. The attachment member 34 is substantially rigid and capable ofsustaining torsional, impact and other loads impressed thereupon by theprosthesis. In addition, the inherent rigidity of attachment member 34prevents it from being distorted in any substantial way and causes theeffective transmission of the aforesaid loads imposed thereupon to asuitable ancillary prosthetic pylon 32.

[0053] With reference to FIG. 2, the attachment member 34 is in thepreferred embodiment vertically oriented so that it may be secured tothe pylon member 32. A coupling device 42 is positioned at the lower endof the pylon member 32 which provides a flat surface upon which thevertical attachment member 34 can be secured. The coupling device 42 hasone attachment surface 44 which mates with the cylindrical outer surfaceof the pylon member 32 and a second substantially flat attachmentsurface 46 which mates with the attachment member 34. In the preferredembodiment, attachment surface 44 is curved to mate with the outersurface of the tubular pylon member 32, and attachment surface 46 isflat to accommodate the forward surface 40 of the attachment member 34.

[0054] Desirably, the coupling device 42 is welded or bonded to thepylon member 32 and has two holes (not shown) into which two bolts 48can be inserted and secured. The attachment member 34 also has two holes(not shown) which align with the holes on the coupling device to placeand secure the two bolts 48 through the attachment member 34 and thecoupling device 42. Other methods of securing the pylon member to thefoot portion are contemplated, such as those disclosed in my priorissued U.S. Pat. No. 5,514,186, the entirety of which is incorporated byreference, as well as those utilizing integrally formed constructions.

[0055] As stated, the attachment member 34 monolithically formed withthe ankle plate 14 is vertically aligned so that it extends relativelydownward from the coupling device 42 on the pylon member 32. As shown inFIG. 2, the thickness of the attachment member 34 along this verticalsection is relatively greater than the thickness of the ankle plate 14substantially horizontally aligned along the foot portion. Theattachment member 34 is also made relatively thicker to support thevertical load imposed on the prosthetic device as well as to restrictundue bending at this juncture. The entire upper vertically-alignedsection of attachment member 34 is preferably of substantially uniformthickness and width.

[0056] The tubular pylon member 32 is preferably removable from theprosthetic device such that the pylon member can be replaced withoutreplacing the remainder of the prosthetic device. This permitsApplicant's invention to be utilized in a broader range of applications.For instance, the tubular member of Applicant's invention can be cut andadapted for use by amputees having different stump lengths includinggrowing amputees. The prosthetist merely needs to cut a standard tubularpylon to the appropriate length. Moreover, this eliminates the need tomanufacture as a part of the prosthesis a long rigid leg section. Thus,fewer materials are needed to manufacture the prosthesis of Applicant'sinvention resulting in reduced manufacturing costs.

[0057] The preferred embodiment further comprises cylindrical slots oropenings 50, 51 in the fore and aft portions of the ankle block 16,respectively, as shown in FIG. 2, to accommodate insertion of stiffeners52, 53. The cylindrical openings 50, 51 are disposed horizontally in adirection generally transverse to a forward walking motion, and betweenupper and lower plate members 22 and 24. Stiffeners 52, 53 can beremovably placed in these openings to provide additional support andrigidity to the prosthetic foot 10, and also to modify the springcharacteristics of the prosthetic foot. For instance, additional energystorage and return can be provided for a more active amputee byinserting stiffeners 52, 53 into ankle block 16 having a higher springconstant. On the other hand, when more control is desired, stiffenerswith a lower spring constant may be inserted to produce an ankle block16 with greater dampening characteristics. Alternatively, thecylindrical openings 50, 51 may remain empty, thereby making thecompliance characteristics dependent solely on the ankle block 16 andthe spring element 18.

[0058] Preferred Materials and Fabrication

[0059] Both the foot plate 12 and the ankle plate 14 are preferablyformed of a flexible material so that flexing of the plates tends torelieve extreme shear stresses applied to the interfaces between theankle block 16 and the plates 12, 14. Both the foot plate 12 and theankle plate 14 are preferably constructed of fiberglass which providesstrength and flexibility. The preferred material for the ankle plate 14and the foot plate 12 is a vinyl ester based sheet molding compound,such as Quantum #QC-8800, available from Quantum Composites of Midland,Mich. Alternatively, the plates may be formed by a plurality of lamninaembedded in an hardened flexible polymer. In other arrangements, theplates may be formed of other materials such as carbon fiber compositesas may be apparent to one skilled in the art. The desirable propertiesof the plates are that they are relatively resilient so as to withstandcracking upon application of repeated bending stresses yet havesufficient flexibility to enhance the performance characteristics feltby the wearer in conjunction with the properties of the resilient ankleblock. The pylon member 32 is preferably made of a stiff material suchas a laminate of fiber reinforced composite. Stiffness in the pylonmember 32 can also be provided by a stiffer and more dense material.

[0060] The ankle block 16 is sandwiched between the foot plate 12 andthe ankle plate 14 as shown in FIGS. 1 and 2 and is preferably bonded toboth plates. The ankle block is preferably formed of urethane, rubber orother suitable material having desired compliance and energy returncharacteristics. A preferred material for the ankle block is expandedpolyurethane foam such as cellular Vulkolka7 Pur-Cell No. 15-50, with adensity of approximately 500 kg/m³ as available from Pleiger PlasticsCompany of Washington, Pa. Alternatively, the ankle block 16 may bemolded or fabricated from a wide variety of other resilient materials asdesired, such as natural or synthetic rubber, plastics, honeycombstructures or other materials. Cellular foam, however, provides a highlevel of compressibility with desirable visco-elastic springiness for amore natural feeling stride without the stiffness drawbacks and limitedcompression associated with solid elastomeric materials. Furthermore,the cellular nature of a foam block makes it lighter than solidelastomers. Foam densities between about 150 and 1500 kg/m³ may be usedto obtain the benefits of the invention taught herein.

[0061] The spring element 18 is preferably made from a highly resilientmaterial that is capable of supporting compression during relativeangular rotation of the upper and lower members 12 and 14, such asduring toe and heel roll, and also vertical compression such as inresponse to vertical shock loads. One preferred material is carbon fibercomposites such as woven fiber mats and chopped fiber in an epoxymatrix. However, other materials with similar strength and weightcharacteristics will be known to those skilled in the art and may beused with efficacy. For instance, other filament types may be used, suchas glass, Kevlar and nylon by way of example, to ensure lightweight andstructural and dynamic characteristics consistent with the needs of aparticular amputee. The wedge 28 may be fabricated from a wide varietyof resilient materials, including natural and synthetic rubber,elastomeric polyurethane, or the like.

[0062] The ankle block 16 containing spring element 18 may be fabricatedby injecting a polyurethane elastomer into a mold allowing it to cure.The spring element 18 may be inserted into the mold prior to injectionof the polyurethane so that during curing, the polyurethane bonds to thespring member. Cylindrical slots or openings 50, 51 for insertion ofstiffeners 52, 53 may be provided in ankle block 16 by insertingcylindrical plugs into the block prior to injection of polyurethane.Alternatively, openings may be provided in the block after curing simplyby cutting or drilling away portions of the ankle block.

[0063] The stiffeners provided in the openings are preferably tubes offoam material having a density chosen according to desired compliancecharacteristics. A preferable material is expanded polyurethane having afoam density between about 150 and 1500 kg/m³. More preferably, adensity of about 250 to 750 kg/m³ is preferred to provide adequateadjustment of the energy storage and return characteristics of the foot.

[0064] Preferred Dimensions

[0065] As illustrated in FIG. 4, the foot plate 12 is preferably ofcurvilinear shape. The thickness t of plate 12 is preferably taperedalong its length, and the tapered profile corresponds approximately tothe weight of the amputee. That is, for a heavier amputee, the thicknessalong the length would be greater than for a lighter weight amputee.Generally, the weight groups may be classified as light, medium, orheavy.

[0066] Table I below presents preferred groupings, as module sizesC/D/E, of cosmesis sizes corresponding to a male “A” width shoe last.The sizes are presented by length L, width B at the forefoot and width Hat the heel of the cosmesis. TABLE I Cosmesis Sizes for Male “A” WidthShoe Last WIDTH B WIDTH H MODULE LENGTH L (cm) (cm) (cm) C 22 2.88 2.1923 3.00 2.25 24 3.12 2.31 D 25 3.25 2.44 26 3.38 2.50 27 3.50 2.56 E 283.62 2.69 29 3.75 2.75 30 3.88 2.81

[0067] Table II below presents preferred module sizes for various weightgroups of TABLE II Modules vs. Weight Groups WEIGHT GROUP MODULE LIGHTMEDIUM HEAVY C CL CM — D DL DM DH E — EM EH

[0068] Table III below presents preferred taper thicknesses (t) for anaverage or “DM” size foot plate 12, taken at position spaced by distancex=1 inch (2.54 cm). TABLE III Taper Thickness t for DM Foot PlatePOSITION (x = 2.54 cm) THICKNESS t (cm) a 0.16 b 0.16 c 0.32 d 0.52 e0.69 f 0.78 g 0.71 h 0.60 i 0.48 j 0.28

[0069] The foot plate 12 has a heel end 54, toward the left in FIG. 4,which is concave-upward or slightly uplifted from a horizontal plane P₁tangential to the heel end 54 of the foot plate 12. Similarly, a toe end56, to the right of FIG. 4, is concave upward or somewhat uplifted froma horizontal plane P₂ tangential to the front portion of the foot plate12. An arch section 58 is formed between the heel and toe ends and ispreferably concave-downward, as shown.

[0070] It is understood that within the cosmesis 30 (not shown), thetangent plane P₁ of the heel end 54 is slightly raised a distance yrelative to the tangent plane P₂ of the toe end 56, as shown. TheDM-sized foot plate of Table III, for example, has y=0.5 inches (1.27cm). The foot plate 12 is preferably 0.25 inches (0.63 cm) from thebottom or sole of the cosmesis 30. The cosmesis 30 may be insert moldedusing an anatomically sculpted foot shape, with details and sizing basedon a master pattern and/or digitized data representing typical footsizes.

[0071] An intermediate region 58 comprising the arch portion of the footplate 12 has the greatest thickness of the foot plate 12. The curvatureof the arch region 58 is defined by the cosmesis or shoe sole profile,and generally corresponds to selected ranges of human foot lengths.

[0072] The foot plate 12 of prosthesis 10 preferably has a lengthbetween about 5 and 15 inches (about 13 and 38 cm), more preferablybetween about 8 and 12 inches (about 20 and 30 cm) for the foot sizesgiven in Table I. The width of foot plate 12 is preferably about 1 to 4inches (about 2.5 to 8 cm). For the example given in Table III for aDM-sized foot plate 12, the length of the plate 12 is approximately 9inches (about 23 cm) and its width is about 2 inches (about 5 cm). Thefoot plate 12 has a thickness between about 0.05 and 0.4 inches (about0.1 and 1 cm), which more preferably may be tapered as indicated inTable III.

[0073] The ankle plate 14 of prosthesis 10 is substantially planar, andis preferably shorter in length than the foot plate 12 and has athickness also defined by the weight group of the wearer. The thicknessof the ankle plate is preferably about 0.05 to 0.4 inches (0.1 to 1 cm).More preferably, the corresponding ankle plate 14 in the present exampleis about 0.2 inches (about 0.5 cm) thick at rear portion 62, tapering toa thickness of about 0.1 inches (about 0.25 cm) at front portion 60. Theankle plate 14 preferably has a length of about 3 to 7 inches (about 8to 18 cm) and a width of about 1 to 3 inches (about 2.5 to 8 cm), morepreferably having length-width dimension of approximately 5×2 inches(about 13×5 cm). The ankle plate 14 is positioned at an angle such thatits front tip 60 is located closer to the foot plate 12 than its reartip 68. Relative to plane P₃ shown in FIG. 4, the rear tip is preferablyraised an angle γ of about 5 to 30 degrees, and more preferably, about10 degrees.

[0074] The ankle block 16 is generally sized such that its upper surfaceis planar and corresponds to the length and width of the ankle plate 14.The lower surface of the ankle block 16 is substantially curvilinear tomate with the curvilinear surface of foot plate 12. In the presentexample, the block 16 has a preferred thickness, at its front 66, ofabout 1 to 3 inches (about 2.5 to 8 cm), more preferably about 1.3inches (about 3.4 cm). Its thickness tapers to a minimum of about 0.5 to1 inch (about 1 to 2.54 cm), more preferably about 0.8 inches (about 2cm) adjacent arch portion 58. The rear 64 of the block 16 is preferablyabout 1 to 4 inches (about 2.5 to 10 cm) thick, more preferably about2.6 inches (about 6.6 cm) thick, which is about twice the thickness ofthe front portion 66 of the block 16. This gives the ankle block asubstantially wedge shape. The greater thickness at the rear of block 16is provided to impart additional support in the rear portion 64 of theankle block due to greater compressive forces on the rear of the footprosthesis caused by off-axis application of force relative to axis 70during heel strike (see FIG. 5A).

[0075] The ankle block 16 may be provided in varying heights orthicknesses, as desired, but is most effective with a thickness ofbetween about 1 and 4 inches (about 2.54 and 10 cm). The front portionand rear surfaces of ankle block 16 are preferably angled according tothe angle γ defined by the plane P₃ and the ankle plate 14. In otherwords, the ankle block has front and rear surfaces which are preferablysloped forward at an angle γ from vertical. The ankle block thusprovides a relatively stiff, yet flexible ankle region which can becustomized for various wearers. Heavier wearers may require a denserresilient material for the ankle block, while lighter wearers mayrequire a less dense material or less thickness.

[0076] As shown in FIGS. 2 and 3, the spring element 18 is positioned inthe ankle block such that the center of the spring element 18, at theposition of fastener 26, is located approximately above the arch portion58 of foot plate 12. The two members 22, 24 of the spring element 18preferably have a constant thickness of about 0.05 to 0.2 inches (about0.1 to 0.5 cm). The distance between the two members at front end 82,when no load is impressed onto the foot 10, is preferably about 0.5 and2 inches (about 1 to 5 cm), more preferably about 0.7 inches (about 1.8cm). At rear end 80, when no load is impressed on the foot 10, thedistance between members 22 and 24 is about 1 to 3 inches (about 2.5 to7.5 cm), more preferably about 1.4 inches (about 3.5 cm). As describedin further detail below, when the foot is in a heel-strike position, therear end 80 of the spring element is compressed. When the foot is in atoe-off position, the forward end 82 of the spring element iscompressed.

[0077] The lengths, widths and thicknesses of the foot plate 12, ankleplate 14, ankle block 16 and spring element 18 may be customized for thewearer according to his/her foot size as well as the approximate weightgroup of the wearer. Likewise, the material choice and size for theseelements may be varied according to the wearer's foot size and weight.

[0078] The cylindrical openings 50, 51 provided in the fore and aftportions of ankle block 16 preferably have a diameter of about 0.1 to0.4 inches (about 0.25 to 1 cm), and more preferably, about 0.2 inches(about 0.5 cm). While the openings 50 and 51 shown in FIG. 2 have thesame diameter, the diameters of the openings may be different toaccommodate different sized stiffeners. For instance, the diameter ofopening 51 may be made larger than the diameter of opening 50 tocorrespond with the greater volume of ankle block 16 in rear portion 64.

[0079] Performance Characteristics

[0080] To more fully explain the improved performance characteristics ofthe present prosthetic foot 10, FIGS. 5A-5D show “snapshots” of aprosthetic foot in several positions of a walking stride. Moreparticularly, FIG. 5A shows a heel-strike position, FIG. 5B shows agenerally flat or mid-stance position, FIG. 5C shows a heel-offposition, and FIG. 5D shows a toe-off position. Throughout the variouspositions shown for a walking stride, the present prosthetic foot 10provides a smooth and generally life-like response to the wearer. Duringa walking stride, the ankle block 16 transmits the forces impartedthereon by the foot plate 12 and ankle plate 14, and experiences agradual rollover, or migration of the compressed region, from rear tofront.

[0081] With specific reference to FIG. 5A, a first position of a walkingstride generally entails a heel strike, wherein the wearer transfers allof his or her weight to the heel of the leading foot. In this case, arear portion 54 of the foot plate 12 comes in contact with a groundsurface 68, albeit through the cosmesis 30. The flexible nature of thefoot plate 12 allows it to bend slightly in the rear portion 54, butmost of the compressive stresses from the weight of the wearer throughthe prosthetic foot 10 to the foot plate 12 are absorbed by a rearregion 64 of the ankle block 16 with spring element 18. The springelement 18 in the rear portion contracts, such that the distance betweenmembers 22 and 24 at rear end 80 decreases. In a front region 66 of theankle block 16, the spring element 18 may expand slightly such that thedistance between members 22 and 24 at front end 82 increases. Frontportion 66 of the ankle block 16 experiences a stretching, or tension,due to the attachment along the entire lower edge of the ankle blockwith the foot plate 12, while rear portion 64 experiences compression.The contraction of the spring element 18 at end 80 and ankle block 16 atend 64 allows the prosthesis 10 to absorb and store energy from thecompressive stresses during heel strike. Further, a slight amount ofbending may occur in a rear region 68 of the ankle plate 14. The rearstiffener 53 between members 22 and 24 is compressed so as to providenecessary support to the foot prosthesis and to prevent separation ofthe members 22, 24 from the wedge 28. Front stiffener 52 is slightlystretched substantially vertically due to the tension forces at frontportion 66 of ankle block 16.

[0082] Next, in FIG. 5B, the wearer reaches a generally flat-footed ormid-stance position, whereby the foot plate 12 contacts the ground 68along substantially its entire length, again through the cosmesis 30. Inthis position the weight of the wearer is directed substantiallydownwardly, so that the compression along the length of the ankle block16 is only slightly greater in the rear portion 64 than in front portion66, due to the off-center application of force. In both the fore andrear ends of spring element 18, the members 22 and 24 are compressedtowards each other, with the rear end 80 being slightly more compressedfrom its original position than the forward end 82. Likewise, stiffeners52 and 53 are compressed due to the downward application of force.Although this view freezes the compressive stress distribution as such,in reality the weight of the wearer is continually shifting from behindthe centerline 70 of the attachment member 34 to forward thereof. Thus,as the wearer continues through the stride, the compression of the ankleblock 16 and the elements embedded within travels from the rear portion64 toward the front portion 66. This migration of the compressed regioncan be termed “rollover.”

[0083] In a next snapshot of the walking stride, FIG. 5C shows theprosthetic foot 10 in a “heel-off” position. This is the instant whenthe wearer is pushing off using ball 72 and toe 74 regions of the foot.Thus, a large compressive force is generated in the front region 66 ofthe ankle block 16, causing the rear region 64 to experience a largeamount of separation or tension. Similarly, the spring element 18 at therear end 80 expands between the two members 22, 24, while it compressesin the front end 82. The front tip 56 of the foot plate 12 may bendsubstantially to absorb some of the compressive stresses. Likewise, thefront tip 60 of the ankle plate 14 may bend somewhat at this point. Itis important to note that although the ankle block 16 absorbs a majorityof the compression generated by the wearer, the foot plate 12 and ankleplate 14 are designed to work in conjunction with the resilient ankleblock and spring element and provide enhanced dynamic performance.Further, the flexing of the foot plate 12 and ankle plate 14 relievessome of the extreme shear stresses applied to the interfaces between theankle block 16 and plates, thus increasing the life of the bonds formedtherebetween. The stiffener 52 located in the front 66 of the ankleblock 16 compresses so as to limit compression of front end 82, givingthe wearer balance and to prevent separation of the members 22, 24 fromthe wedge 28. Stiffener 53 extends due to the separation of ankle block16 in rear portion 64.

[0084] In FIG, 5D, a final position of the walking stride is shown,wherein the prosthetic foot 10 remains in contact with the ground 68,but some of the weight of the wearer is being transferred to theopposite foot, which has now moved forward. In this “toe-off” position,there is less bending of the front tip 56 of the foot plate 12 and lesscompression of the front portion 66 of the ankle block 16 and front end82 of spring element 18. Likewise, the front tip 60 of the ankle plate14 may flex a slight amount, depending on the material and thicknessutilized. The region of highest compression of the ankle block 16remains at the farthest forward region 66, but it is reduced from thecompression level of the heel-off position of FIG. 5C. Thus, the rearportion 64 of the ankle block 16 experiences a small amount of tensionor spreading.

[0085] It can now be appreciated that the “feel” of the presentprosthetic foot is greatly enhanced by the cooperation between the footplate, ankle plate, ankle block and spring inserts. As the wearercontinues through the walking stride the dynamic response from theprosthetic foot is smooth as the ankle block with spring insertscompresses in different regions. Further, the flexing of the ankle andfoot plates assist in smoothly transmitting the various bumps and jarsfound in uneven walking surfaces.

[0086] Alternative Embodiments

[0087] It will be appreciated that many alternative embodiments of aprosthetic foot having features and advantages in accordance with thepresent invention may also be constructed and used with efficacy. Onesuch alternative embodiment is shown in FIG. 6. Reference numerals forFIG. 6 generally correspond to the reference numerals used in FIGS. 1-5Dfor like elements. Thus, the prosthetic foot 10 shown in FIG. 6generally comprises a lower foot plate 12, an upper, smaller ankle plate14, an ankle layer or block 16 made of resilient material, connectingthe foot plate 12 to the ankle plate 14, and a spring element 18embedded within the ankle block. The foot plate 12 has a length andwidth roughly equal to the approximate length and width of theparticular wearer's amputated foot and sized to fit within an outer,flexible cosmesis 30, shown in phantom. As shown in FIG. 6, the ankleplate 14 has a substantially arcuate curvature extending from theintegrally formed attachment member 34 to the front of the ankle plate14.

[0088] More particularly, the spring element 18 as illustrated in FIG. 6is a resilient support member inserted within the resilient ankle block16. The spring element 18 shown in FIG. 6 is preferably a plate-likemember with a curvilinear concave downward shape and a substantiallyrectangular vertical projection. The spring element 18 is preferablymade from a carbon fiber composite material such as describedhereinbefore, although other similar materials may be used as well.

[0089]FIG. 7 illustrates another alternative embodiment of theinvention. Again, like reference numerals are generally used to indicatelike elements. Thus, the prosthetic foot 10 shown in FIG. 7 generallycomprises a lower foot plate 12, an upper, smaller ankle plate 14, andan ankle layer or block 16 made of resilient material, such as solid orfoam rubber or polyurethane, and connecting the foot plate 12 to theankle plate 14. The foot plate 12 has a length and width roughly equalto the approximate length and width of the particular wearer's amputatedfoot and sized to fit within an outer, flexible cosmesis 30, shown inphantom. As shown in FIG. 7, the ankle plate 14 transitions into asubstantially arcuate or curved ankle section 36 which is preferablyintegrally formed between the attachment member 34 and the ankle plate14.

[0090]FIG. 8 illustrates yet another alternative embodiment of theinvention. Again, like reference numerals are generally used to indicatelike elements. Thus, the prosthetic foot 10 shown in FIG. 8 generallycomprises a lower foot plate 12, an upper, smaller ankle plate 14, andone or more ankle blocks 16 a, 16 b made of resilient material, such assolid or foam rubber or polyurethane, and connecting the foot plate 12to the ankle plate 14. If desired, the posterior ankle block 16 a mayhave a density or compliance characteristic which is different than thatof the anterior ankle block 16 b, so as to render it more soft and morecompliant, for example, than the anterior ankle block 16 b. Forinstance, this configuration could provide a more compliant heelresponse during heel strike.

[0091] Ankle blocks 16 a, 16 b may be formed integrally or separately,as desired or as expedient. Preferably, they are positioned closelyadjacent to one another so as to occupy substantially the entire spacebetween the foot plate 12 and the ankle plate 14. The foot plate 12preferably has a length and width roughly equal to the approximatelength and width of the particular wearer's amputated foot and sized tofit within an outer, flexible cosmesis 30, shown in phantom. As shown inFIG. 8, the ankle plate 14 transitions into a substantially arcuate orcurved ankle section 36 which is preferably integrally formed betweenthe attachment member 34 and the ankle plate 14.

[0092]FIGS. 9 and 10 illustrate two other possible alternativeembodiments of the invention. Again, like reference numerals aregenerally used to indicate like elements. Thus, the prosthetic foot 10shown in FIG. 9 generally comprises a lower foot plate 12, an upper,smaller ankle plate 14, and, in this case, an inflatable bladder 19disposed between the foot plate 12 and the ankle plate 14. The bladder19 has the further advantage in that it enables the patient orprosthetist to vary the performance characteristics of the prosthesis byadjusting the pressure in the bladder 19. This may be accomplished, forexample, through the provision of a valve means 21, which is provided incommunication with the bladder 19. In a preferred embodiment, the valve21 is adapted to receive a needle from an air pump (not shown) or from aCO₂ cartridge (described with respect to FIG. 16B below), and may besuitably disposed on bracket 27, as illustrated in FIGS. 9 and 10. Thevalve 21 may be operatively connected to bladder 19 via tubing or othersuitable communication passage.

[0093] The bladder 19 may be secured via adhesive or other suitableaffixing means to the upper ankle plate 14 and the lower foot plate 12so as to provide substantially the sole means of connection and supporttherebetween. Optionally, one or more retaining straps 23 may be used toprovide primary or secondary connection support, as needed or desired.Strap 23 may be fabricated from any number of suitably tough, flexiblematerials such as epoxy-impregnated canvas or the like. For example,straps 23 may be operatively attached to the forefoot portion of theprosthetic foot 10 as illustrated in FIG. 9 via adhesive, or nuts andbolts, or may be releasably attached around the structural member 12, 14through the provision of Velcro7-type fasteners or similar expedient.

[0094] The straps 23 provide a number of benefits. For example, ifjuxtaposed to a bladder member 19, the strap may be appropriatelytightened to “flatten” the bladder, thus increasing the contact areabetween the structural members 12, 14 and the bladder. Moreover,restraining means such as the straps 23 may be incorporated to restrictthe distance that the associated structural members 12, 14 may move fromone another. The straps 23 may also be utilized to prevent undesirableexcessive loading and stressing of the structural members 12, 14 and/orthe bladder 19.

[0095] The bladder 19 is preferably fabricated from a suitably strong,flexible, leak-proof, lightweight material such as urethane or the like.By way of example, the bladder may be formed by heat sealingappropriately sized and shaped pieces of urethane sheet to each other.Suitable thicknesses of urethane sheet material have been found to be0.01 to 0.02 inches (0.25-0.50 mm), but a wide range of suitablethicknesses and materials may also be utilized with efficacy. Bladderpressures of up to 80 psi (5.5 bar) have been utilized with efficacy.

[0096] The bladder 19 is preferably enwrapped in a covering material ofKevlar or similarly strong material to prevent the bladder 19 fromexploding under high pressures and to help define the final inflatedshape of the bladder. In preferred embodiments, a covering may includetop and bottom sections which are stitched together at the perimeter 25of the bladder 19. Those skilled in the art will understand that avariety of covering materials and methods of fabrication and assemblythereof may be also utilized with efficacy, without departing from theteachings of the invention.

[0097] Bladder 19 may enclose air, CO₂, or a similar gas-like substance,or may alternatively enclose liquids or gels such as water, silicone, orthe like. Any such assembly is preferably selected and adjusted toprovide the desired deformability and consequent “cushioning” effect orenergy-storing, absorption and release.

[0098] The bladder 19 may comprise a single chamber bladder, asillustrated in FIG. 9, or, optionally, it may comprise a multiplechamber bladders with or without venting provided between adjacentchambers. For example, the bladder could be bifurcated into anterior andposterior chambers or portions 19 a, 19 b such that the posteriorportion 19 a can be adjusted to have a compliance characteristic whichis different than that of the anterior portion 19 b, so as to render itmore soft and more compliant, for example, than the anterior portion.This may be desirable, for instance, to provide a more compliant heelresponse during heel strike. If desired or expedient, the bladder 19 maybe tapered in shape so as to permit operative and proper alignment ofthe bladder between the ankle plate 14 and the foot plate 12.

[0099] Optionally, a spring element identical or similar to thatillustrated and described above in connection with FIGS. 2-5, may beprovided substantially completely within the bladder 19 (FIG. 9) so asto provide primary or supplemental support between the foot and ankleplates, as desired. For, example, the spring element may comprise tworelatively flat carbon fiber composite members secured at their middleand separated at their ends. This gives the spring element a preferableshape of a bow tie or double wishbone. During walking, the combinationof the resilient spring element and inflatable bladder provides a smoothand adjustable rollover characteristic from a heel-strike to a toe-off,as desired.

[0100] The foot plate 12 preferably has a length and width roughly equalto the approximate length and width of the particular wearer's amputatedfoot and sized to fit within an outer, flexible cosmesis 30, shown inphantom. As shown in FIGS. 9 and 10, the ankle plate 14 transitions intoa substantially arcuate or curved ankle section 36 which is preferablyintegrally formed between the attachment member 34 and the ankle plate14.

[0101]FIG. 11A illustrates another prosthetic foot 10 similar to thatdescribed in FIGS. 1-4 above, but with several modifications asdescribed below. Accordingly, the prosthetic foot 10 of FIG. 11Agenerally comprises a lower foot plate 12, an upper, smaller ankle plate14, an ankle layer or block 16 made of resilient material, connectingthe foot plate 12 to the ankle plate 14, and cylindrical slots orcavities 50 and 51 allowing for the insertion of optional stiffeners 52and 53 (see FIGS. 11B-11D). The foot plate 12 has a length and widthroughly equal to the approximate length and width of the particularwearer's amputated foot and sized to fit within an outer, flexiblecosmesis 30, shown in phantom. As shown in FIG. 11A, the ankle plate 14has a substantially arcuate curvature extending from the integrallyformed attachment member 34 to the front of the ankle plate 14.

[0102] The ankle block 16 of FIG. 11A preferably has a front surfacethat is sloped from the front edge of the ankle plate 14 forward to thefoot plate 12 there below. Similarly, the rear surface of the ankleblock 16 is preferably also sloped in a forward direction from the rearof the ankle plate 14 in a forward direction to the foot plate 12. Astrap 23 such as described above is provided around the ankle plate 14,ankle block 16 and foot plate 12, preferably over a rear portion of theprosthetic foot.

[0103] FIGS. 11B-11D show three examples of stiffeners that can beinserted into the cavities 50 or 51. FIG. 11B illustrates a stiffener 52(or 53) that is substantially cylindrical in shape and is comprisedsubstantially entirely out of foam. FIG. 11C shows a similar cylindricalstiffener 52, having a cylindrical opening 96 extending therethrough andopen on each end such that the stiffener is hollow and has asubstantially tubular configuration. The size of the opening 96 can bevaried to achieve a desired degree of compliance for the stiffener 52.FIG. 11D illustrates a stiffener 52 defining a cylindrical cavity 96therein being closed at each ends. A tube 98 is connected to the cavity96 such that air or another gas or fluid can flow into and out of theopening to provide a desired pressure within the opening to control thedegree of compliance of the stiffener. Thus, the opening 96 serves as aninflatable bladder. One or more valves (not shown) may be connected tothe tube 98 to regulate the flow of air into and out of the bladder 96.

[0104]FIG. 12 illustrates another embodiment of a prosthetic foot 10similar to that shown in FIG. 11A, except that in FIG. 12 there areprovided two ankle plates 14 and 15 layered on top of one another insliding arrangement. The top plate 14 is preferably monolithicallyformed from a high strength composite material with a curvilinear anklesection 36 and an upper attachment area 34, such as described above. Thebottom plate 15 is also preferably monolithically formed with acurvilinear ankle section 37 and an upper attachment area 35. The upperattachment areas 34 and 35 are preferably attached to pylon member 32through coupling device 42, with bolts or screws (not shown) extendingthrough the upper attachment areas 34 and 35 and coupling device 42 intothe pylon member 32.

[0105] The lower plate 15 preferably extends forward past the front ofankle plate 14, and more preferably the plate 15 extends to the front ofthe ankle block 16. Strap 23 a secures the plates 14 and 15, the ankleblock 16 and the foot plate 12 at the rear of the ankle block. Strap 23b secures the plates 14 and 15 at the front of the plate 14. Byproviding an upper and lower plate 14 and 15, respectively, these platesare capable of bending and sliding relative to each other. Thisadvantageously reduces the bending resistance of the prosthesis whilemaintaining adequate vertical support strength.

[0106]FIGS. 13 and 14 illustrate another alternative embodiment for aprosthetic foot 10 similar to the embodiment shown in FIG. 10 above.Thus, the foot 10 generally comprises a lower foot plate 12, an upper,smaller ankle plate 14, and a plurality of inflatable bladders disposedbetween the foot plate 12 and the ankle plate 14. More preferably, arear or heel bladder 19 a is provided near the rear of the ankle plate14, and a pair of toe bladders 19 b which are in fluid communicationwith each other are provided at the front of the ankle plate (see FIG.14). A strap 23 is provided at the rear of the ankle plate 14surrounding the bladder 19 a and foot plate 12. Optionally, plates 29 a,29 b, 29 c and 29 d may be provided between each of the bladders and theankle plate 14 and/or foot plate 12.

[0107] The pressure in the heel bladder 19 a is controlled by valve 21a, while pressure in the toe bladders 19 b is controlled by valve 21 b.It will be appreciated that although FIG. 13 shows one valve 21 bcontrolling the pressure in both toe bladders 19 b, it is alsocontemplated that each toe bladder 19 b may be controlled by separatevalves. The valves 21 a and 21 b may be operatively connected to thebladder via tubing or other suitable communication passages. In theembodiment shown in FIG. 13, tubings 17 a and 17 b connect the heelbladder 19 a and toe bladders 19 b, respectively, to the appropriatevalves. Beyond the valves 21 a and 21 b, the tubings 17 a and 17 b arepreferably joined, with a single tubing 17 c extending away therefrom toa gas or air input/output source 21 d. A valve 21 c controls thepressure through the tubing 17 c.

[0108] It will be appreciated that the valve control system describedwith respect to FIGS. 13 and 14 may be used with other types ofinflatable bladders. For instance, valves such as FIGS. 13 and 14 may beused to inflate a stiffener 52 such as illustrated in FIG. 11D above.Furthermore, separate tubings may be used to adjust pressure in multiplestiffeners provided in an ankle block as described with respect to FIG.11A.

[0109] FIGS. 15A-16A illustrate another embodiment of a prosthetic foot10 incorporating an air pump system for actively or passivelycontrolling pressure within inflatable bladders. The components of thissystem are shown in FIG. 15A. A syringe type air pump 90 is providedwith an air intake port 92 having a check valve. The syringe pump 90 isconnected by a tube 88 to an accumulator 86. The accumulator 86 isconnected by a tube 85 to an electronic control system 84 including avalve manifold. Also connected to the control system 84 are an air vent87, and tubes 83a and 83b providing fluid communication to inflatablebladders 19 a and 19 b, respectively.

[0110] These components are collectively arranged into a prosthetic foot10, shown in FIG. 16A. It will be appreciated that the arrangement ofcomponents in FIG. 16A is purely exemplifying and thus otherarrangements are possible as well. As described in other embodimentsabove, the inflatable bladders 19 a and 19 b are provided between ankleplate 14 and foot plate 12. Connected to the upper attachment area 34 ofthe prosthetic foot 10 are a pair of schematically shown telescopingpylons 95 and 97. Further details regarding telescoping and other typesof pylons that may be used in conjunction with the embodiments of thepresent invention are described below and in applicant's copendingapplication entitled SHOCK MODULE PROSTHESIS, Ser. No. 09/289,533, filedApr. 19, 1999, and U.S. Pat. No. 5,458,656, the entirety of each ofwhich are hereby incorporated by reference. Lower pylon 95telescopically engages upper pylon 97, such that pylons 95 and 97 arepreferably slidingly and rotationally interengaged with each other.Preferably, a resilient element, such as a coil compression spring, isproximally fixed within upper pylon 97 and distally fixed within lowerpylon 95. Thus, when a force is applied to the prosthetic foot, thepylons 95 and 97 move toward one another in a compressed configuration.When the force is released, the pylons move apart to a restconfiguration.

[0111] The syringe 90 preferably includes a plunger 91 and a cylinder93. Plunger 91 is attached to the upper pylon 95, such as with bracket99 or other means. Cylinder 93 is preferably similarly attached to thelower pylon 97. Control system 84 and accumulator 86 are also preferablyattached to lower pylon 97. Accordingly, when force is applied to theprosthetic foot 10, the relative movement of the pylons causes theplunger 91 to move in and out of the cylinder 93 and produce airpressure through the tube 88. Air is preferably drawn through a filterelement comprising air intake port 92 (not shown in FIG. 16A). The fluidis stored in accumulator 86 and passed on to the valve manifold of theelectronic control system 84. The manifold preferably electronicallycontrols how much air is provided to each of the inflatable bladders 19a and 19 b, and also how much air will be vented out through tube 87.Thus, the pump system of FIGS. 15A-16 uses pressure built up by theamputee's own motion and determines an appropriate pressure to beprovided to each of the inflatable bladders.

[0112] For example, FIG. 15B illustrates schematically one embodimentfor the valve manifold of the control system 84. When the bladders 19 aand 19 b require more air for additional support, the control system 84opens valves 103, 105 and 107 to allow air to pass from the accumulator86 to the bladders 19 a and 19 b through tubes 83 a and 83 b. When it isdesired to deflate bladders 19 a and 19 b, the valve 101 can be openedand valve 103 can be closed so that air passes from the bladders 19 a,19 b through tubes 83 a and 83 b and out tube 87. In addition, when oneof the bladders requires more or less air than the other, valves 105 and107 can be selectively adjusted to individually inflate or deflatebladder 19 a or 19 b, with either valve 101 or valve 103 remaining open.The valves can be sensed and controlled electronically or via acomputer. It will be appreciated that a variety of valve configurationsmay be employed to selectively adjust the appropriate pressure for thebladders 19 a and 19 b.

[0113] It will further be appreciated that although FIG. 16A depicts thesyringe as being attached externally to the pylons, the syringe may alsobe attached internally to the pylons. Furthermore, other components ofthe pump system, such as the accumulator and the valve manifold, mayalso be provided within the pylons. One such embodiment is described byFIG. 23, below.

[0114]FIG. 16B illustrates another prosthetic foot incorporating aninflatable bladder 19 and a CO₂ cartridge for adjusting the pressurewithin the bladder. The embodiment of FIG. 16B is similar to theprosthetic foot of FIG. 9, and includes an inflatable bladder 19sandwiched between an upper ankle plate 14 and a lower foot plate 12. Apylon 32 is attached to the ankle plate 14 through a vertically orientedupper attachment member 34 and a curvilinear ankle section 36, all ofwhich are preferably monolithically formed. A CO₂ cartridge 132 ispreferably attached to the exterior surface of the pylon 32, and isconnected to the bladder 19 through a fluid line 134 having a valve 21.The valve 21 in one embodiment is electrically controlled, with apressure sensor to control the amount of CO₂ delivered to the bladder.

[0115]FIG. 17 shows another embodiment of a prosthetic foot 10. Thisembodiment is similar to that shown in FIG. 12 above in that itgenerally comprises two ankle plates 14 and 15, an ankle block 16 and afoot plate 12. However, in the prosthetic foot 10 of FIG. 17, the plates14 and 15 both extend to the front of the ankle block 16. Furthermore,the ankle plate 16 is more preferably a chambered urethane having aplurality of openings extending therethrough. Specifically, in additionto the cylindrical slots 50 and 51, the ankle block 16 of FIG. 17 alsohas an opening 55 that is substantially oblong when viewed from the sideand that extends across the transverse dimension of the ankle block 16.Similar to the embodiments described above, the opening 55 can be filledwith other materials for adjusting the stiffness of the block. Openingscan be enclosed, if desired, defining closed chambers filled with acompressible fluid such as air.

[0116]FIG. 18 shows a similar embodiment to that of FIG. 17, except thatthe ankle block 16, in addition to the cylindrical slots 50 and 51, hasthree additional openings 55 a, 55 b and 55 c. More preferably, slots 55a and 55 c are cylindrical similar to slots 50 and 51, while slot 55 bhas a substantially dual concave-out shape when viewed from the side.All five of these openings can remain empty or may be filled withstiffeners and/or fluid as described above. It will be appreciated thatthe number and shapes of these openings may be varied giving dueconsideration to the goals of the desired prosthetic foot. None, some orall of the openings filled may be filled with stiffeners, in order toobtain desired performance characteristics for the foot 10.

[0117]FIG. 19 illustrates another embodiment of a prosthetic foot 10.Like the embodiments described above, this foot includes two ankleplates 14 and 15, an ankle block 16 and a foot plate 12. The ankle block16 also includes cylindrical slots 50 and 51 similar to those describedabove. Within the slots 50 and 51 are inserted cams 112 and 114 thatrotate about shafts 113 and 115, respectively. These rotatable cams,when inserted, cause the shape of the slots to deform elliptically incompliance with the shape of the cams. This in turn adjusts thecompliance of the ankle block depending on the orientation of each ofthe cams. Thus, as shown in FIG. 19, one cam may be oriented such thatits cross-section is aligned substantially transversely relative to aforward walking motion, while the other cam may be oriented such thatits cross-section is aligned substantially parallel to a forward walkingmotion. These cams may be rotated while within the ankle block 16 todifferent orientations as well.

[0118] The cams are preferably made from a material stiffer than that ofthe ankle block 16, and more preferably, made be made of metal or othermaterials. Thus, inserting a cam into the ankle block 16 increases thestiffness of that part of the ankle block. Moreover, as shown in FIG.19, when one cam 112 is oriented substantially transversely to a forwardwalking motion, and another cam 114 is oriented substantially parallelto a forward walking motion, the transverse cam 112 preferably impartsgreater stiffness to that part of the ankle block than does the othercam 114. Furthermore, because the cams are rotatable, the stiffness ineach portion of the ankle block is adjustable. It will also beappreciated that although FIG. 19 shows only two cams, fewer or greaternumber of rotatable cams can also be incorporated into the ankle block.

[0119]FIG. 19 also illustrates a strap 110 attached to the rear face ofupper attachment area 35 of ankle plate 15. This strap 110 preferablyextends down and is attached to the foot plate 12. The strap 110advantageously is provided to adjust the relative flexing propertiesbetween the ankle plates and the foot plate and to control the maximumdistance between the respective plates. It will be appreciated that thestrap shown in FIG. 19 may be incorporated in any of the embodimentsabove in which an ankle support member is provided between an ankleplate and a foot plate.

[0120]FIG. 20 illustrates another embodiment of a prosthetic foot 10. Inthis embodiment, the ankle block 16 includes a front chamber 119 and arear chamber 121, each containing a stiffener 118 and 120, respectively,arranged transversely therein relative to a forward walking motion. Thechambers 119 and 121 are sized to allow the stiffeners 118 and 120 tomove forward and backward relative to a forward walking motion withineach of the chambers. Thus, as shown in FIG. 20, when the stiffeners aregenerally circular when viewed from the side, each of the chambers hasan oblong shape. By being able to move the stiffeners 118 and 120 withinthe ankle block 16, a user can selectively adjust the stiffness of theprosthetic foot by changing the position of the stiffeners.

[0121] In the embodiment shown in FIG. 20, the stiffeners 118 and 120are cylindrical rods which are attached to arms 122 and 124,respectively. These arms are joined in a middle chamber 117 by anactuator 116, schematically shown in FIG.

[0122] In one embodiment, the actuator 116 is a motor that preferablyadjusts the location of the stiffeners 118, 120 in the chambers 119, 121to provide desired stiffness in a particular location of the ankle block16. The motor 116 may, for example, be a manual or servo motor. In oneembodiment, the arms 122 and 124 are integrally formed such that aconstant distance is maintained between the front stiffener 118 and therear stiffener 120. The motor 116 then adjusts the position of the armssuch that the stiffeners are in the same relative position within eachof their respective chambers.

[0123] It will be appreciated that other embodiments are also possible.For instance, the stiffeners need not be separated by a constantdistance, and can be adjustable to shorten or lengthen the distancetherebetween. This may be accomplished, for example, by providing theactuator 116 as a knob that can be turned in one direction to shortenthe distance between the stiffeners and in the other direction tolengthen the distance between the stiffeners. In such an embodiment, thearms 122 and 124 may be opposingly threadingly engaged with the actuator116. Furthermore, it will be appreciated that where the actuator 116 isa knob, the stiffeners can be separated by a constant distance withintegrally formed arms 122 and 124, with the knob capable of beingturned to adjust the location of the stiffeners within their respectivechambers while maintaining a constant distance therebetween.

[0124]FIG. 21 illustrates another embodiment of a prosthetic foot 10.Similar to the embodiments above, this prosthetic foot 10 includes anankle block 16 disposed between ankle plates 14 and 15 and foot plate12. The ankle block 16 preferably includes a single cylindrical slot 50in the fore portion of the block, the slot 50 including a stiffener 52therein. It will be appreciated, however, that additional slots may beprovided in the ankle block 16 as described above.

[0125] As shown in FIG. 21, the ankle block 16 preferably includes inthe rear portion a wedge cut-out 125 adjacent to and extending to thefoot plate 12. The cut-out 125 is preferably disposed directly below thepylon 32 to correspond substantially to the location of a human heel.More preferably, a wedge piece 126 is inserted into the cut-out 125 ofthe ankle block 16 to provide additional support in the heel portion ofthe prosthetic foot 10. In one embodiment, as shown in FIG. 21, thewedge piece 126 has a rear surface that is substantially flush with therear surface of the ankle block and has a convex shape that mates withthe wedge cut-out 125. The wedge piece is preferably fabricated fromurethane rubber, although other materials may be used as well. Becausethe wedge piece 126 is removable from the ankle block 16, wedge piecesof varying stiffness may be inserted into the wedge cut-out to providedesired degrees of stiffness in the heel. For example, a wedge piecethat has a stiffness that is greater or less than that of the ankleblock may be inserted into the wedge cut-out. It will also beappreciated that using wedge pieces of different sizes and shapes mayalso provide desired compliance characteristics. Thus, the prosthesismay be used without a wedge piece 126, or with a wedge piece of varyingsize or stiffness to adjust the performance characteristics of theprosthesis.

[0126]FIG. 21 also illustrates a strap 110 incorporated with anadjustment mechanism connected to the pylon 32. A housing 128 for thestrap is provided on the rear surface of the upper attachment area 35,the housing having a slot 129 extending vertically therethrough. Thestrap 110 is preferably able to move through the slot 129 in order totighten or loosen the connection with the foot plate 12, as indicated bythe arrows shown in the figure. Within the slot 129 the strap can beheld and locked in place by any appropriate means, such as a press-fit,screws, pins, brackets, etc. FIG. 22 further illustrates that an insert,such as a C-shaped insert 130, can be placed within adjacent andconnecting portions of the strap 110 to further adjust the tension inthe strap.

[0127] In another embodiment, a syringe-type air pump system similar tothat shown in FIGS. 15A-16 is produced by the action of the telescopingpylons as shown in FIG. 23. In such an embodiment, an inner pylon 214acts as the plunger of the syringe, and an outer pylon 212 acts as thecylinder of the syringe. As the inner pylon 214 is compressed anddecompressed toward and away from the outer pylon 212 with a spring 220or other compression member, fluid pressure is generated within achamber defined between the two pylons. When the inner pylon 214 is theupper of the two pylons, the inner pylon is preferably sealed at the topof the chamber, and the outer pylon is preferably sealed at the bottomof the chamber. More preferably, the sealing of the chamber may beprovided using valves 224, 248 to regulate fluid flow into and out ofthe chamber. A valve 248 provided at the bottom of the chamber in theouter pylon preferably leads to a fluid reservoir 250, which may beprovided within the outer pylon or separately therefrom. As with theaccumulator above, the reservoir 250 may be connected via a fluid line236 to an inflatable bladder 206 that supports a prosthetic foot.

[0128] More particularly, FIG. 23 illustrates a prosthetic foot 200having an inflatable bladder similar to that shown in FIG. 9. Similar tothe prosthetic foot described above, the prosthetic foot 200 generallycomprises a lower foot plate 202, an upper, smaller ankle plate 204, andan inflatable bladder 206 disposed between the foot plate 212 and theankle plate 214. The bladder 206 is preferably secured to the platesthrough straps 208, or by other means as described above.

[0129] The pressure in the bladder 206 is controlled through connectionto an active shock module 210. Shock module 210 includes outer pylon 212and inner pylon 214, shaped and adapted for smooth relative motion.Pylons 212 and 214 are preferably slidingly and rotationallyinterengaged with each other while retaining their operative horizontalalignment with each other through a relatively close fit between theinside dimensions of outer pylon 212 and the outside dimensions of innerpylon 214. The inner pylon 214 has an enlarged outside diameter at itsproximal end, approximately equal to the outside diameter of the outerpylon 212. This enlarged diameter portion of the inner pylon 214therefore extends beyond the proximal end of the outer pylon 212 anddoes not extend into the outer pylon 212.

[0130] Pylon 214 also has a female pyramid fitting 216 at its proximalend, for attachment to a stump socket (not shown). Outer pylon 212preferably has a cylindrical outer surface to facilitate the attachmentof various types of prosthetic feet using conventional prostheticcouplers. For example, the lower end of pylon 212 may be attached toprosthetic foot 200 via a pyramid coupler 218 and female pyramid fitting220. The female coupler 218 is slipped over the lower extremity of theouter pylon 212 and clamped into position.

[0131] Shock module 210 preferably includes a hybrid spring-fluidresilient element, comprising an internal coil compression spring 220 incombination with a compressible fluid such as air. Spring 220 ispreferably proximally fixed with respect to inner pylon 214 and distallyfixed with respect to outer pylon 212 via spring support 222.Optionally, a valve 224 is provided within pylon 214 to vary thepressure of the fluid inside of shock module 210. A torque-resistingcuff 226 provides torsion-resistance to the prosthesis and also keepsdirt and other debris from getting between pylons 212 and 214 andaffecting their relative motion. Further details on shock modules thatmay be used in conjunction with the embodiments of the present inventionmay be found in U.S. application Ser. No. 09/556,249, entitled ACTIVESHOCK MODULE PROSTHESIS, filed Apr. 24, 2000, the entirety of which ishereby incorporated by reference.

[0132] An end cap 228 is preferably provided below the spring support222 within the outer pylon 212. Both the end cap 228 and the springsupport 222 are preferably threaded to engage an internally threadedsurface 230 of the outer pylon 212. Both the spring support 222 and theend cap 228 preferably have an internal hole 232, 234, respectively,which allows the compressible fluid to pass therethrough to a fluidreservoir 250, described below. A cover cap 238 preferably seals thehole 232, 234 below the end cap 228. This cover cap is preferablythreadingly engaged with a second internally threaded surface 240 of theouter pylon 212, the second internally threaded surface 240 having alarger diameter than that of the first internally threaded surface 230.Along the surface that secures end cap 228, the cover cap 238 isprovided with an O-ring notch 242 that abuts against the horizontalsurface 244 between the surfaces 230 and 240. By providing an O-ring 246into this notch, when the cover cap is screwed into the internallythreaded surface 240 against the horizontal surface 244, the O-ring 246is compressed to provide a seal with respect to the interior of pylon212.

[0133] The cover cap 238 preferably includes a valve 248 to control thepassage of fluid from inside the inner pylon to a reservoir 250contained within the outer pylon. This reservoir is defined on its sidesby the internally threaded surface 240, at one end by the cover cap 238,and at its other end by a reservoir cap 252 which is also threadinglyengaged in the surface 240. Below the threaded surface 240 the bottom ofthe outer pylon 212 on its inside surface 254 is preferably nonthreaded,and the reservoir cap 252 has a larger diameter portion at its bottomthat abuts against the horizontal surface 256 between surfaces 240 and254. An O-ring notch 258 is provided in the reservoir cap, and O-ring260 is inserted into the notch which compresses against horizontalsurface 256 to form a fluid tight seal.

[0134] The torque-resisting cuff 226 is preferably configured tooscillate between a relatively straight vertical position, when theouter pylon and inner pylon are moved relatively far apart, and a curvedposition, when the outer pylon and inner pylon are compressed relativeto one another. FIG. 23 illustrates the shock module 210 in a fullycompressed configuration such that the cuff 226 is curved and the innerpylon 214 extends as far as possible into the outer pylon 212. Moreparticularly, when fully compressed the enlarged outer diameter portionof the inner pylon 214 preferably abuts against the proximal end of theouter pylon 212.

[0135] Similar to the syringe system described with respect to FIGS.15A-16A above, the telescoping pylons of the active shock module 210generate pressure within the bladder 206 by the amputee's motion causingthe pylons to move toward and away from each other. More particularly,the relative motion of the pylons, in conjunction with the compressiblefluid and/or spring or other compressible medium inside the pylons,causes fluid pressure to build up within the inner pylon. Pressure mayalso be regulated within the inner pylon through the valve 224. Valve248 at the bottom of the inner pylon regulates fluid pressure and can beopened to transfer fluid into the reservoir 250. Fluid line 236preferably connects the reservoir to the bladder 206, and valve 264controls the flow of fluid into the bladder in order to adjust thepressure inside the bladder. It will further be appreciated thatpressure step-up or amplification may be provided by changing therelative sizing of the telescoping pylons.

[0136] It will be appreciated that although the active shock module hasbeen described with respect to inflatable bladder 206, the shock modulemay also be used with other inflatable members, such as the stiffener ofFIG. 11D. Furthermore, an active shock module may be used to inflatemultiple members, such as shown in FIGS. 10, 13, and 14.

[0137] Although this invention has been disclosed in the context ofcertain preferred embodiments and examples, it will be understood bythose skilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Thus, it is intended that the scope of the present inventionherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

What is claimed is:
 1. A prosthetic foot comprising: a foot plate, thefoot plate comprising a resilient material capable of flexing along itslength; an ankle plate spaced from the foot plate and disposed generallyabove the foot plate; a fore ankle block comprising a compressiblematerial and disposed below the ankle plate; and an aft ankle blockcomprising a compressible material and disposed below the ankle platebehind the fore ankle block; wherein the foot plate includes acantilevered heel portion.
 2. The prosthetic foot of claim 1, whereinthe ankle block material is relatively soft.
 3. The prosthetic foot ofclaim 1, wherein the heel portion extends rearward from the aft ankleblock.
 4. The prosthetic foot of claim 1, wherein the foot platecomprises a fore portion and an aft portion, and the fore and aftportions comprise a unitary whole.
 5. The prosthetic foot of claim 4,wherein the fore ankle block is sandwiched between the ankle plate andthe fore portion of the foot plate, and the aft ankle block issandwiched between the ankle plate and the aft portion of the footplate.
 6. The prosthetic foot of claim 1, wherein the fore ankle blockand the aft ankle block have different compliance characteristics. 7.The prosthetic foot of claim 6, wherein the aft ankle block is morecompliant than the fore ankle block.
 8. The prosthetic foot of claim 1,wherein the foot plate and the ankle blocks flex in a cooperative mannerto provide substantially smooth and continuous rollover transition fromheel-strike to toe-off.
 9. The prosthetic foot of claim 1, wherein thefoot plate has a tapered thickness along its length, such that thethickness increases from a heel section to an arch section and decreasesfrom the arch section to a toe section.
 10. The prosthetic foot of claim1, wherein the ankle plate has a tapered thickness along its length,such that the thickness increases from a forward portion to a rearwardportion.
 11. The prosthetic foot of claim 1, wherein the ankle plate isintegrally formed with an upwardly extending attachment section.
 12. Aprosthetic foot comprising: a foot plate, the foot plate comprising aresilient material capable of flexing along its length; an ankle platespaced from and disposed generally above the foot plate; and an ankleblock comprising a compressible material disposed below the ankle plate,the ankle block being subdivided into at least two separate portions,including a fore portion and an aft portion; wherein the foot plateincludes a cantilevered heel portion.
 13. The prosthetic foot of claim12, wherein the ankle block material is relatively soft.
 14. Theprosthetic foot of claim 12, wherein the cantilevered heel portionextends rearward of the aft ankle block portion.
 15. The prosthetic footof claim 12, wherein the foot plate comprises a fore portion and an aftportion, and the fore and aft portions comprise a unitary whole.
 16. Theprosthetic foot of claim 12, wherein the fore ankle block portion andthe aft ankle block portion have different compliance characteristics.17. The prosthetic foot of claim 12, wherein the aft ankle block portionis more compliant than the fore ankle block portion.
 18. A prostheticfoot comprising: a foot plate, the foot plate comprising a resilientmaterial capable of flexing along its length; an ankle plate spaced fromand disposed generally above the foot plate; and an ankle blockcomprising at least two portions of compressible material disposedclosely adjacent one another and disposed below the ankle plate; whereinat least one of the ankle block portions is formed of a material havinga compliance characteristic that is different from a compliancecharacteristic of at least one other of the ankle block portions. 19.The prosthetic foot of claim 18, wherein at least one of the ankle blockportions is formed of a material that is relatively soft.
 20. Theprosthetic foot of claim 18, wherein the foot plate comprises a toeportion and a heel portion, and the toe and heel portions comprise aunitary whole.
 21. The prosthetic foot of claim 20, wherein the footplate has a tapered thickness along its length, such that the thicknessincreases from the heel section to an arch section and decreases fromthe arch section to the toe section.
 22. The prosthetic foot of claim18, wherein at least one of the ankle block portions is made of a foammaterial having a density between about 150 and 1500 kg/m³.
 23. Theprosthetic foot of claim 22, wherein at least one of the ankle blockportions is made of a foam material having a density of about 500 kg/m³.24. The prosthetic foot of claim 18, wherein the ankle block providessubstantially the sole means of support and connection between the footplate and the ankle plate.